It's actually upstream. I ran the same:
$ make bindeb-pkg
on the upstream source as I did on the Debian source, and yes, it gave me .deb packages.
Here's the repo for the upstream script that was part of the problem:
https://github.com/torvalds/linux/commits/master/scripts/package/builddeb
Note the recent changes.
I may be wrong, and it's a Debian patch that is causing the problem, but from what I've seen of the code it's
probably upstream. I suppose I could download an upstream version of 6.7, and verify it has the same problem,
but since nobody on the Debian maintainer side seems to care, I won't bother.